MRI is an ideal imaging tool for guiding and monitoring prostate cancer biopsy and local therapy. The high sensitivity and specificity to focal prostate lesions and abnormalities, combined with real-time monitoring of the delivery process and subsequent physiological changes hold great potentials. Unfortunately, closed high-field MRI scanners, the most superior imaging systems, have been unavailable for interventions. The strong magnetic field and confined physical space present formidable challenges, and "conventional" difficulties such as needle deflection, tissue deformation, and target motion add to the problem. Our teams have established the clinical and technical feasibility for MRI-guided prostate biopsy and therapy. We are proposing to translate this technology outside the confines of our specialized research hospitals. In particular, we will develop a technology platform for precise trans-perineal needle placement into the prostate for both diagnostic and therapeutic purposes;inside conventional (high-field closed) MRI scanners, under real-time image guidance and monitoring. This system will be uniformly applicable to'a wide range of MRI scanners, supporting long bore, short bore, and open magnets of high and low fields alike. The initial applications will be prostate biopsy and low-dose-rate Brachytherapy. This system will be robust, simple, and operable by a multi-disciplinary team of physicians. Toward this goal, we propose a BRP between the Brigham and Women's Hospital, Johns Hopkins University, and CMS Image Guidance Division (formerly Burdette Medical). Our teams have complimentary strengths in MR guided interventions, robotics, and prostate cancer treatment with intraoperative dosimetry. A research triangle has been in de-facto existence for several years and produced shared technology, publications, and inventions;supported by government grants. The Brigham group established the clinical feasibility of MR guided transperineal prostate biopsy and brachytherapy, funded by RO1-5R01AG019513-03 (PI Tempany). The Hopkins team created an in-MRI prostate robot currently in human trials for biopsy and seed placement, co-funded by R01-EB002963-01 (PI: Fichtinger). The Burdette group developed a commercial prostate cancer brachytherapy suite with over 60 installations worldwide, co-funded by NIH grants 5R44CA088139-04 and 1R43CA099374-01 (PI: Burdette). Strong results, multidisciplinary expertise, and existing partnerships support our proposal.